Nickel coatings were obtained from Watts bath containing sodium dodecyl sulfate (SDS) or polyvinylpyrrolidone (PVP) surfactants by direct current plating. The influence of electrolysis parameters, temperature, current density, concentration of surfactants and pH on the nickel deposits brightness is investigated through a multiple linear regression model with interaction. The models obtained fitted very well the experimental data. ANOVA statistical analysis shows that all design factors are significant, and the brightness of nickel deposits obtained from bath containing PVP is more sensitive to the changes in the factors levels. The electrochemical behaviour of baths was discussed; the results revealed an inhibitive effect exerted by both SDS and PVP. We have also found that the brightness and the inhibition are well linked and directly proportional. In addition, the corrosion resistance of the nickel coatings was slightly improved, especially with PVP. Finally, the optimization analysis showed that PVP could efficiently and eco-friendly substitute SDS as an additive of nickel electroplating.
The effects of thiourea (TU) on the kinetics and electrochemical nucleation of tin from stannous chloride bath in acidic medium have been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry. CV results showed that the tin reduction is a one-step reaction and indicated that TU inhibited the reduction of tin ions at high concentration. EIS analysis showed that the electrodeposition process of tin is affected by the addition of TU. The nucleation mechanism of tin was studied using both Sharifker-Hills (SH) and Palomar-Pardavé (PP) models. SH model indicated that hydrogen evolution and tin reduction occurred simultaneously. Non-dimensional current-time transients curves based on PP model revealed that the tin nucleation followed 3D progressive mechanism without TU and with 0.01 M TU, while the nucleation process changes to 3D instantaneous in presence of 0.1 M TU. However, at 1 M TU, the nucleation mechanism is located between instantaneous and progressive model. The proton reduction reaction was inhibited at all concentrations of TU. Quantitative determination showed that in the presence of TU, the diffusion coefficient of tin species, the hydrogen evolution rate constant, the nucleation rate constant and the number of active sites were decreased.
Daphne gnidium L. (DGL), a plant known to be rich source of polyphenols, a naturally occurring class of antioxidants, was tested for its ability to play the role of primary and secondary brighteners for electrodeposition of nickel, as a replacement for synthetic brighteners such as glycerol and formaldehyde. A simple and convenient approach was adapted consisting in adding an accurate amount of powdered leaves of Daphne gnidium L. (DGLP) or Daphne gnidium L. leaves extract (DGLE), to the Watts bath, to play the role of brightening agents. Cyclic voltammetry studies revealed that DGLP could inhibit the reaction of nickel reduction and improve the quality of the deposits as efficiently as glycerol and formaldehyde. SEM analyses showed that the micro-cracks decreased and sometimes disappeared from nickel deposits prepared in the presence of DGLP as a brightener. The results of this study show that DGL can be used satisfactorily, with minimum operations as a brightening agent for nickel electrodeposition. The key idea of direct immersion of DGLP in the Watts bath, aimed to the replacement of synthetic brighteners and the reduction of the overall cost of nickel electrodeposition.
The structural, elastic and thermodynamic properties of the manganese monocarbide in ZnS (B3) phase were investigated using the DFT calculation with the PBE functional. The ground state properties of this materials such as lattice constant, bulk modulus, pressure derivatives of bulk modulus and Young’s modulus are calculated and the obtained results show a good agreement with the experimental data. Moreover, the estimated values of elastic constants indicate that the studied material is found to be mechanically stable. The results show also that the heat capacity of this materials as a function of the temperature is close to the Dulong-Petit limit (49.6 J/mol.K)at higher temperatures. The thermal expansion( α) and Debye parameter were also calculated at the different temperatures. The pressure effects on the above parameters were computed and their values are compared with the experimental results.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.